1. Field of the Invention
The invention relates to a device for measuring an angle at which a magnetic field is aligned in a plane relative to a reference axis, with at least two magnetic field sensors which are aligned with their measurement axes in and/or parallel to the plane and oriented perpendicular to each other. The invention further relates to a method for measuring an angle, at which a magnetic field is aligned in a plane relative to a reference axis, wherein a first magnetic field component and a second magnetic field component aligned perpendicular thereto are measured in and/or parallel to the plane.
2. Description of Related Art
A device of the aforesaid type is disclosed in Reymond, S. et al., “True 2D CMOS integrated Hall sensor”, IEEE SENSORS 2007 Conference, pp. 860-863, which has a semiconductor substrate in which are integrated so-called vertical Hall sensors as magnetic field sensors 64. The magnetic field sensors are equidistantly arranged relative to each other on a circular ring residing in the chip plane of the semiconductor substrate in such a way that the planes in which the magnetic field sensors extend are always radially aligned relative to an imaginary center axis, which passes through the center point of the circular ring and is aligned at right angles to the chip plane. The magnetic field sensors are connected to a scanning device in such a way that the measurement signals of the individual magnetic field sensors are capable of being applied successively to a differential output terminal for a rotation scanning signal. Cyclically rotating, successive scanning of the magnetic field sensors is thus carried out. The differential output terminal is connected via a differential amplifier to a low pass integrated in the semiconductor substrate. By means of the low pass, the analog output signal of the amplifier is smoothed to an approximately sinusoidal signal. The zero crossing of the analog measurement signal thus achieved is determined, and the angle at which a magnetic field flowing through the semiconductor substrate in the chip plane is aligned relative to a reference axis is determined from the zero crossing point.
A disadvantage resides in the device in that the scanning of the many magnetic field sensors is time-consuming. In spite of the complex circuitry, the device enables only a small band width. A further disadvantage resides in the fact that the non-degenerative, analog low pass must meet stringent requirements in terms of linearity and frequency response, which entails a considerable use of surface area on the chip and a high power consumption.
A device of the aforementioned type is also disclosed in DATA SHEET UZZ9001, Sensor Conditioning Electronics Product Specification, Philips Semiconductors, 27 Nov. 2000, which has two magnetoresistive sensors integrated as magnetic field sensors in a semiconductor chip, which are aligned with their measurement axes in a plane at right angles relative to each other. Each magnetic field sensor is in each case connected to an analog-digital convertor, which is configured as a sigma-delta modulator. A decimation filter, at whose output is emitted a magnetic field measurement value in the form of a 15 bit digital word, is always disposed downstream relative to each analog-digital convertor. The digital words are transmitted to a calculator, which calculates the angle at which a magnetic field flowing through the semiconductor substrate is aligned in the chip plane relative to a reference axis from the arctangent of the quotient of the digital words. The relatively highly complex circuitry is also disadvantageous herein. The calculation of the magnetic field angle results in a latency, which poses a disadvantageous when the device is used in a control circuit.
The object is therefore to create a device of the aforesaid type which enables a simple construction and a high measurement precision. A further object is to design a method of the aforesaid type with which the angle can be easily determined with high precision.